Well, after 2 years of service I have decided to adjust R19 and R21 to be sure to have the best of my babies (especially now that I have 2 brand new DIY speakers that really deserve it (JP3 ribbon tweeter with audiotechnology 18H52 and audiotechnology 10C102 : a sarastro like speaker ! ))
What I found is that I had only 2.3 as bias value. And this is a maximum value I think as the heatsinks temperature is about 60°C (despite the fact that my heatsinks are huge, but...).
The DC after the filter is 44.7V.
My speaker are 4 ohms. And I think they are something like 89db.
What current gain should I choose then ? I know nelson recommand 50%, but then with my low bias and according to the well known excel file for calculating power, the power at 8 ohms is 84.6 W and at 4 ohms it is only 42.3 W !
At 70% I would have 105,1 W at 8 ohms and 117,6 W at 4 ohms
At 60%, 105 W 8 R; 66 W 4 R
I don't know what to choose on the paper, as a starting point. Do you have any idea on the side effects of setting the AC current gain as high as 70% ??
What I found is that I had only 2.3 as bias value. And this is a maximum value I think as the heatsinks temperature is about 60°C (despite the fact that my heatsinks are huge, but...).
The DC after the filter is 44.7V.
My speaker are 4 ohms. And I think they are something like 89db.
What current gain should I choose then ? I know nelson recommand 50%, but then with my low bias and according to the well known excel file for calculating power, the power at 8 ohms is 84.6 W and at 4 ohms it is only 42.3 W !
At 70% I would have 105,1 W at 8 ohms and 117,6 W at 4 ohms
At 60%, 105 W 8 R; 66 W 4 R
I don't know what to choose on the paper, as a starting point. Do you have any idea on the side effects of setting the AC current gain as high as 70% ??
Hi,
I wouldn´t go higher than 60-65%. Just try as it´s an easy adjustment.
I´ve put some sockets in the resistor holes so I can swap ac-current-gain resistors very fast. This way you can listen for what you like best.
It really depends on the load what sounds best.
The other (more expensive) option would be to lower the supply voltage as it is a bit too high for the bias your running. 35V would be more than enough in your case.
William
I wouldn´t go higher than 60-65%. Just try as it´s an easy adjustment.
I´ve put some sockets in the resistor holes so I can swap ac-current-gain resistors very fast. This way you can listen for what you like best.
It really depends on the load what sounds best.
The other (more expensive) option would be to lower the supply voltage as it is a bit too high for the bias your running. 35V would be more than enough in your case.
William
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